A contactor is a breaking and closing device for frequently closing, carrying and breaking normal current and overloaded current. It is applied on electric power, power distribution and power applications. In electric engineering, since a contactor can quickly disconnect the AC and DC main circuits and connect an apparatus to a large current control circuit, contactors are often used for controlling motors, also used for controlling electrical loads, such as factory equipment, electric heaters, machine tools and a variety of electric power phase units. A contactor not only can close and break a circuit but also has a protective effect on low-voltage release. The contactor has a large control capacity, and is adapted to frequent operation and remote control, therefore it is one of the important components in automatic control systems. When used in different situations, contactors with different rated operational currents are needed. However, the insulating housings of all the phases of a traditional contactor are integral to each other, not absolutely independent from each other, so that it is impossible to improve the rated operational current of the contactor by increasing parallel connections.